Theoretical investigation of the thermoelectric transport properties of BaSi 2

In order to investigate the mechanism of the electron and phonon transport in a silicon nanotube (SiNT), the electronic structures, the lattice dynamics, and the thermoelectric properties of bulk silicon (bulk Si) and a SiNT have been calculated in this work using density functional theory and Boltzmann transport theory. Our results suggest that the thermal conductivity of a SiNT is reduced by a factor of 1, while its electrical conductivity is improved significantly, although the Seebeck coefficient is increased slightly as compared to those of the bulk Si. As a consequence, the figure of merit (ZT) of a SiNT at 1200 K is enhanced by 12 times from 0.08 for bulk Si to 1.10. The large enhancement in electrical conductivity originates from the largely increased density of states at the Fermi energy level and the obviously narrowed band gap. The significant reduction in thermal conductivity is ascribed to the remarkably suppressed phonon thermal conductivity caused by a weakened covalent bonding, a decreased phonon density of states, a reduced phonon vibration frequency, as well as a shortened mean free path of phonons. The other factors influencing the thermoelectric properties have also been studied from the perspective of electronic structures and lattice dynamics.

Section: Thermoelectric Propertiessupporting

confidence: 49%

“…The group velocity of carriers υ e (E) is calculated by differentiating the energy with respect to the wave vector in the Brillouin zone. [26] Consequently, the electrical conductivity and the Seebeck coefficient are defined as [27][28][29] σ…”

Section: Calculation Methodsmentioning

confidence: 99%

A comparison study on the electronic structures, lattice dynamics and thermoelectric properties of bulk silicon and silicon nanotubes

Lu¹,

Qu²,

Cheng³

2013

“…[33] The constant relaxation time approximation, [34] which assumes τ to be energyindependent, is used to estimate the transport properties, and this approximation has successfully predicted the transport properties for many thermoelectric compounds. [18][19][20][21][35][36][37][38] To get reasonable transport properties, a more dense k-mesh (35×35×1) was used for WSe 2 monolayer in the Monkhorst-Pack scheme, and it can guarantee convergence and obtain accurate carrier group velocities, which is essential for determining the electrical transport properties of WSe 2 monolayer.…”

Section: Methodsmentioning

confidence: 99%

Biaxial strain-induced enhancement in the thermoelectric performance of monolayer WSe ₂

Shen

Nie

2017

The effects of biaxial strain on the electronic structure and thermoelectric properties of monolayer WSe 2 have been investigated by using first-principles calculations and the semi-classical Boltzmann transport theory. The electronic band gap decreases under strain, and the band structure near the Fermi level of monolayer WSe 2 is modified by the applied biaxial strain. Furthermore, the doping dependence of the thermoelectric properties of n-and p-doped monolayer WSe 2 under biaxial strain is estimated. The obtained results show that the power factor of n-doped monolayer WSe 2 can be increased by compressive strain while that of p-doping can be increased with tensile strain. Strain engineering thus provides a direct method to control the electronic and thermoelectric properties in these two-dimensional transition metal dichalcogenides materials.

“…The firstprinciples calcualtions, as a kind of theoritical method, have successfully described the electronic structures and the thermoelectric properties of many materials. [18][19][20] 3. Results and discussion…”

Section: Computational Detailsmentioning

confidence: 99%

Electronic structures and thermoelectric properties of solid solutions CuGa_1−xIn_xTe₂: A first-principles study

Li¹,

Xu²,

Yi³

2014

The electronic structures of solid solutions CuGa 1−x In x Te 2 are systematically investigated using the full-potential all-electron linearized augmented plane wave method. The calculated lattice parameters almost linearly increase with the increase of the In composition, which are in good agreement with the available experimental results. The calculated band structures with the modified Becke-Johnson potential show that all solid solutions are direct gap conductors. The band gap decreases linearly with In composition increasing. Based on the electronic structure calculated, we investigate the thermoelectric properties by the semi-classical Boltzmann transport theory. The results suggest that when Ga is replaced by In, the bipolar effect of Seebeck coefficient S becomes very obvious. The Seebeck coefficient even changes its sign from positive to negative for p-type doping at low carrier concentrations. The optimal p-type doping concentrations have been estimated based on the predicted maximum values of the power factor divided by the scattering time.